PFAS contaminated asphalt and concrete - Knowledge gaps for future research and management.

Per- and polyfluoroalkyl substances (PFAS) are now widespread in the environment. Globally, airfields and paved firefighting training surfaces are particularly affected due to extensive use of aqueous film forming foams (AFFF). This PFAS contamination in exposed concrete and asphalt has not been widely addressed. This review focusses on PFAS interaction with concrete and asphalt, traversing extraction, analytical identification/quantification, PFAS fractionation via differential adsorption on organic and inorganic substrates, and reuse options for contaminated concrete and asphalt. A total of 24 knowledge gaps and management challenges for concrete and asphalt characterisation and management have been identified.

Effect of aquifer storage and recovery (ASR) on recovered stormwater quality variability.

Aquifer Storage and Recovery (ASR) is increasingly being considered as a means of reusing urban stormwater to supplement available urban water resources. Storage of stormwater in an aquifer has been shown to affect water quality but it has also been claimed that storage will also decrease the stormwater quality variability making for improved predictability and management. This study is the first to document the changes in stormwater quality variability as a result of subsurface storage at four full scale ASR sites using advanced statistical techniques. New methods to examine water quality are required as data is often highly left censored and so traditional measures of variability such as the coefficient of variation are inappropriate. It was observed that for some water quality parameters (most notably E. coli) there was a marked improvement of water quality and a significant decrease in variability at all sites. This means that aquifer storage prior to engineered treatment systems may be advantageous in terms of system design to avoid over engineering. For other parameters such as metal(loids)s and nutrients the trend was less clear due to the numerous processes occurring during storage leading to an increase in variability, especially for geogenic metals and metalloids such as iron and arsenic. Depending upon the specific water quality parameters and end use, use of ASR may not have a dampening effect on stormwater quality variability.

Application of a risk management framework to a drinking water supply augmented by stormwater recharge.

The Blue Lake is an important water resource for the city of Mount Gambier and the surrounding region, primarily as the drinking water supply source, but also as a tourist attraction. Mount Gambier's stormwater is discharged directly via drainage wells into the unconfined, karstic Gambier Limestone aquifer, which in turn provides the majority of recharge to Blue Lake. Discharge of urban runoff to the aquifer commenced in the 1800s as a means of stormwater management, but is now recognised as contributing to the drinking water supply in Blue Lake. Recently, guidelines for managing the risks associated with water recycling and augmenting drinking water supplies have been developed. This paper examines the organic chemical hazards associated with a stormwater to potable recycling scheme as an example of the current risk management framework.

Managed aquifer recharge: rediscovering nature as a leading edge technology.

Use of Managed Aquifer Recharge (MAR) has rapidly increased in Australia, USA, and Europe in recent years as an efficient means of recycling stormwater or treated sewage effluent for non-potable and indirect potable reuse in urban and rural areas. Yet aquifers have been relied on knowingly for water storage and unwittingly for water treatment for millennia. Hence if 'leading edge' is defined as 'the foremost part of a trend; a vanguard', it would be misleading to claim managed aquifer recharge as a leading edge technology. However it has taken a significant investment in scientific research in recent years to demonstrate the effectiveness of aquifers as sustainable treatment systems to enable managed aquifer recharge to be recognised along side engineered treatment systems in water recycling. It is a 'cross-over' technology that is applicable to water and wastewater treatment and makes use of passive low energy processes to spectacularly reduce the energy requirements for water supply. It is robust within limits, has low cost, is suitable from village to city scale supplies, and offers as yet almost untapped opportunities for producing safe drinking water supplies where they do not yet exist. It will have an increasingly valued role in securing water supplies to sustain cities affected by climate change and population growth. However it is not a universal panacea and relies on the presence of suitable aquifers and sources of water together with effective governance to ensure human health and environment protection and water resources planning and management. This paper describes managed aquifer recharge, illustrates its use in Australia, outlining economics, guidelines and policies, and presents some of the knowledge about aquifer treatment processes that are revealing the latent value of aquifers as urban water infrastructure and provide a driver to improving our understanding of urban hydrogeology.

Factors affecting the performance and risks to human health of on-site wastewater treatment systems.

Aerobic wastewater treatment systems (aerobic systems) are the preferred choice in a region overlying a karstic aquifer used for drinking water supplies, as they are thought to provide better protection to groundwater and human health than standard septic systems. However, aerobic systems in operation do not always perform to design standard; while this is often blamed on lack of maintenance, few studies have investigated the link directly. This study investigates the performance of domestic on-site wastewater treatment systems in South Australia, and compares effluent quality to maintenance records. Effluent from 29 septic tanks and 31 aerobic systems was analysed for nutrients, physico-chemical parameters and microbiological indicators. Aerobic systems generally provided greater treatment than septic tanks, yet most aerobic systems did not meet regulatory guidelines with high levels of indicator bacteria in 71% of samples. The effect of system size, number of household occupants and maintenance on aerobic system treatment performance was analysed: chlorine levels were positively correlated with time of last service, and nutrient concentrations were positively correlated with the number of occupants. A microbial risk assessment revealed the observed irrigation practices to be high risk; and sufficient residence time in the aquifer cannot be guaranteed for protection of groundwater used for drinking. Additional preventive measures such as irrigation management or post treatment of drinking water supply (such as UV disinfection) are required to meet public health targets.

A critical evaluation of combined engineered and aquifer treatment systems in water recycling.

Australian experience at five research sites where stormwater and reclaimed water have been stored in aquifers prior to reuse, have yielded valuable information about water treatment processes in anaerobic and aerobic aquifers. One of these sites is the stormwater to potable water ASTR project at the City of Salisbury, a demonstration project within the broader EC project 'RECLAIM WATER'. A framework for characterising the effectiveness of such treatment for selected organic chemicals, natural organic matter, and pathogens is being developed for inclusion in new Australian Guidelines for Management of Aquifer Recharge. The combination of pre-treatments (including passive systems such as reed beds) and aquifer treatment effectiveness in relation to source waters and intended uses of recovered water will be described. Advantages and disadvantages of various types of pre-treatments in relation to effectiveness and sustainability of managed aquifer recharge will be discussed taking account of aquifer characteristics. These observations will be consolidated into a draft set of principles to assist in selection of engineered treatments compatible with passive treatment in aquifers.